Many fluids are transported in bulk containers, such as ISO tanks and shipping containers, railcar containers, 55 gallon drums, and other bulk containers. Highly viscous fluids present particular transportation problems for Flexi Tanks: ease of discharge of a filled container.
Non-limiting examples of highly viscous fluids includes pepper mash (or other vegetable or fruit mash), syrups, such as corn, palm oil or other vegetable oils such as olive oils, inks, resins, cooking oils and lubricants. During transportation, these types of products will become more viscous because of the reduction in product temperature resulting from exposure to ambient temperature conditions. Upon arrival at the discharge location, this increase in product viscosity presents problems. The lower product temperature and viscosity often makes it impossible to pump or gravity discharge the product.
To assist in unloading containers filled with highly viscous products, heat can be applied to the container holding the product to indirectly increase the product temperature and therefore reduce the product viscosity. Enough heat has to be applied to make the product capable of flowing. As an example, TOD/Charlie Nelson/Cargill has developed a heater pad that is placed underneath a flexible shipping container before shipment. Upon reaching the unloading point, the pad is filled with a heating media such as low pressure steam or hot water, and heat transferred from the pad to the container, then to the product in the container by thermal conduction. However, the heating pad and Flexi Tank are constructed of a polymer material and therefore are poor conductors of heat energy. Additionally, because there is no movement or agitation of the product inside the container, this method is relying on the convective transfer of energy to the product inside the container, and results in inefficient heat transfer. Because of the materials of construction of the Flexi Tank/Heater Pad and the lack of fluid motion in the Flexi Tank, the overall heat transfer coefficient is extremely low. For this reason, this method is very time and energy intensive. Because of the existing inefficiencies, heat transport in a viscous fluid can be slow and inefficient, and hence, smaller containers, such as a 300 gallon container, are used to reduce the fluid volume to be heated. Even with these smaller containers, heat time and discharge times can still be excessive.
In an effort to improve the efficiency of this heat transfer, agitation can be imparted into the product in the container. Gas (e.g. air) injection is one method used to mix products inside containers. See U.S. Pat. No. 4,595,296 to Parks (incorporated by reference). More specifically, Chris White (U.S. patent application Ser. No. 11/326,738, now U.S. Pat. No. 7,744,268) has developed a method to mix viscous products inside of a flexible container using gas injection, ultimately reducing the energy and time needed to heat a product to a flowing state (hereby incorporated by reference).